NullPointerException occures when openning Properties without a given re...

...source

an additionan null check is added for the result of getResource() call. The following usages of
the result has such checks, so now it's being checked before the first use.

see: https://issues.jboss.org/browse/JBIDE-18260

Signed-off-by: vrubezhny <vrubezhny@exadel.com>